Customise an existing Wordpress Theme to fit a slightly different layout/design

We have a premium Wordpress Theme from ThemeForest called Invictus - http://themes.doitmax.de/wordpress/invictus/ and we need to customise the navigation area to fit a slightly different layout.

We also need to customise the Homepage footer area slightly.

We're looking for someone who can do a professional job without disturbing the rest of the site.

We have a layered PNG to work from but I've included a jpg to show the layout so you can compare it to the theme before responding.

We'll certainly have more customising work if everything runs smoothly!

Thanks